NORTH AMERICA INCLUDES THE COUNTRIES of Canada, the United States, and Mexico, as well as the world’s largest island, Greenland. During the last Ice Age, a great sheet of ice flowed across the continent scouring the landscape, deepening the depressions that now hold the Great Lakes, and dumping fertile soil onto the central plains. The Rocky Mountains form the backbone of the continent, running from Alaska to New Mexico. In the east are the Appalachian Mountains, flanked by coastal lowlands to the east and south. In eastern Canada lies the Canadian Shield, a huge basin of ancient eroded rocks now covered with thin soils. Deserts stretch from the southwestern United States down into northern Mexico.

MOUNTAIN RANGES
The main mountain ranges of North America, the snowcapped Rockies and the forested Appalachians, vary greatly in appearance (see above cross-section). The difference can be explained by their age. The Rockies, shown right, are relatively young mountains that have not yet been worn down. The Appalachians, however, are among the world’s oldest mountains and have been gradually eroded by the scouring action of wind, water, and the movement of glaciers.

erode [ɪ'rəǔd] разрушать; разъедать; размывать
acid erodes metals — кислота разъедает металлы
the sea is eroding the southern shore line of the island — море размывает южный берег острова
coastal ['kəust(ə)l] - береговой, прибрежный
range - диапазон, разнообразие
a voice with an extraordinary range — голос с необыкновенно широким диапазоном
a wide range of goods/prices — широкий ассортимент товаров, большой разброс цен
a wide range of interests/problems — широкий круг интересов/проблем
soil I [sɔɪl] / 1) грунт, земля, почва
barren / poor soil — бесплодная, бедная почва
clay soil — глинистый грунт
fertile soil — плодородная почва
gradually [grædʒʊəlɪ] постепенно
Their relations gradually changed. — Их отношения постепенно изменялись.

The great canyon
The Grand Canyon was formed over millions of years as the waters of the Colorado River and its tributaries carved their way through the solid rock. At some points the canyon is 1 mile (1.6 km) deep, and cuts through rocks that are 2,000 million years old. Different types of fossils found in the canyon walls reveal the dates of its changing history.

The great plains
Across the center of Canada and the US lie the Great Plains, also called the prairies. This huge area has hot summers and cold, snowy winters. Trees are rare except along rivers and lake shores, but the region was once covered with grasses grazed by millions of buffalo. Today, little natural prairie survives, and in its place farmers cultivate vast fields of corn and wheat.

The great lakes
Estimated to contain one-fifth of the world’s freshwater, the five Great Lakes straddle the border between Canada and the US. Only Lake Michigan, shown left, lies entirely within the US. The lakes are linked by waterways and drained by the St. Lawrence River, which empties into the Atlantic Ocean. The Niagara River, which joins lakes Erie and Ontario, passes over the famous Niagara Falls.